In the manufacture of detergent formulations for laundering and general purpose washing operations, it is common practice to employ detergent builders -- substances used in combination with surface-active compounds to aid in cleansing the articles being washed. The polyphosphates, notably sodium tripolyphosphate and tetrasodium pyrophosphate, are the commonly used detergent builders. However, these materials possess a serious shortcoming. For example, the phosphorus residues resulting from the widespread use of synthetic detergent formulations containing these phosphorus-containing builders have been said to contribute to eutrophication of rivers, lakes, underground streams, and other bodies of water. ["Detergent Phosphorus Effect on Algae" by Thomas E. Maloney, Journal of the Water Pollution Control Federation, Vol. 38, No. 1, pp. 38-45 (January 1966)]. To appreciate the magnitude of the problem, it has been estimated that over two billion pounds of salts of condensed phosphates are used in detergents each year in the United States. The phosphorus-containing builders can therefore be properly termed ubiquitous.
Further there is also at present a growing need for low cost sequestering agents efficiently operable over wide pH ranges (7-10). The use of sequestering agents to remove metal ions or to reduce metal ion concentrations is well known to the scientific community. For example, sequestering agents are used in metal cleaning processes, leather tanning, textile processes, the stabilization of dyes and vegetables oils, laundering and other washing operations, and the processing of beer. Most of the sequestering agents used today are efficient only at a high pH (9-10). In addition some of the best known sequestering agents such as sodium tri-polyphosphate suffer from the eutrophication problems discussed above.
Thus, there is a need for a compound which is an effective non-phosphorus detergent builder and is also an effective sequestrant over a wide pH range. Accordingly, it is an object of this invention to provide a detergent builder system which is devoid of the eutrophic characteristics exhibited by the polyphosphates and other phosphorus builders. Further, it is an object of this invention to provide washing compositions which are devoid of phosphorus-containing builders but which possess the advantageous characteristics of washing compositions which presently contain the polyphosphate builders. Another object of this invention is to provide a sequestering agent which is effective over a wide pH range.
Other important objects of this invention will become apparent from the ensuing description and appended claims.